Rotary drilling methods employing a drill bit and drill stems have long been used to drill wellbores in subterranean formations. Drilling fluids or muds are commonly circulated in the well during such drilling to cool and lubricate the drilling apparatus, lift drilling cuttings out of the wellbore, and counterbalance the subterranean formation pressure encountered. The recirculation of the drilling mud requires the fast and efficient removal of the drilling cuttings and other entrained solids from the drilling mud prior to reuse. Shaker separators are commonly used to remove the bulk solids from the drilling fluid.
The bulk solids removed from the drilling fluid by shaker separators often include hydrocarbons, either from the drilling fluid, the wellbore, or both. Such oily cuttings typically cannot be discharged into the environment directly from the shaker due to the negative impact of the hydrocarbon material on the environment, as well as the value associated with the drilling fluid. Further, cuttings that are oil wet or water wet are often difficult to handle. Thus, a drying operation for drill cuttings is often implemented as a secondary operation to the shaker separator to remove residual drilling fluid from the cuttings.
Vertical, centrifugal separators are often used to dry the cuttings before discharge or collection. In general, vertical separators, or material dryers, include a housing containing a drive mechanism to which is connected both a flight assembly and a screen assembly. The separator further includes an inlet for induction of the material to be separated. Material directed into the separator is captured by the flight and screen assemblies, separation occurring as the material migrates downwardly with a liquid component and/or very small particles being forced outwardly through a fine mesh screen into a space between the screen and the housing by centrifugal force. The majority of the liquids are then drawn off and the solids are generally ejected from an outlet assembly located below the rotor drive assembly. Material that is discharged from the separator exits through a solids outlet assembly portion of the separator. Due to the centrifugal force used to remove the liquid component of the material, during discharge the solid component tends to be flung outward and in the direction of rotation of the flight and screen assemblies. This often causes an accumulation of solid material in the solid outlet assembly which must periodically be removed to avoid backup of material propagating from the outlet assembly into the area between the flight and screen assemblies. To clean the solids outlet assembly requires stopping operation of the separator for the time required to clean out the assembly. It would therefore be an improvement to have an automatic cleaning apparatus that could clean and maintain the outlet assembly during normal operation of the separator. An additional advantage of such a system would be an improvement in the efficiency of the separator to treat material by increasing the effective online production time as well as maintaining a sufficient opening for solids to be discharged out of the separator before material back-up can diminish the separating efficiency of the flight and screen assembly.